/*
 * Copyright (C) 2016 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.graph;

import static com.google.common.graph.GraphConstants.EXPECTED_DEGREE;

import com.google.common.collect.BiMap;
import com.google.common.collect.HashBiMap;
import com.google.common.collect.ImmutableBiMap;
import java.util.Collections;
import java.util.Map;
import java.util.Set;

/**
 * An implementation of {@link NetworkConnections} for undirected networks.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <E> Edge parameter type
 */
final class UndirectedNetworkConnections<N, E> extends AbstractUndirectedNetworkConnections<N, E> {

    protected UndirectedNetworkConnections(Map<E, N> incidentEdgeMap) {
        super(incidentEdgeMap);
    }

    static <N, E> UndirectedNetworkConnections<N, E> of() {
        return new UndirectedNetworkConnections<N, E>(HashBiMap.<E, N>create(EXPECTED_DEGREE));
    }

    static <N, E> UndirectedNetworkConnections<N, E> ofImmutable(Map<E, N> incidentEdges) {
        return new UndirectedNetworkConnections<N, E>(ImmutableBiMap.copyOf(incidentEdges));
    }

    @Override
    public Set<N> adjacentNodes() {
        return Collections.unmodifiableSet(((BiMap<E, N>) incidentEdgeMap).values());
    }

    @Override
    public Set<E> edgesConnecting(Object node) {
        return new EdgesConnecting<E>(((BiMap<E, N>) incidentEdgeMap).inverse(), node);
    }
}
